The signs went up about a half-century ago, but they spring to memory like yesterday. On a white background, in vivid red lettering: “Danger” and “KEEP OUT.”

An unseen hand mounted the warnings around the top and sides of the wide concrete tunnel, an underpass built to allow tiny Coal Creek to flow under Pacific Coast Highway and into Santa Monica Bay. The subtext couldn’t have been clearer: “Stay Off Our Beach.”

That’s not the kind of message anyone wants to read. It was especially unwelcome to us, kids lucky enough to grow up in the sunbaked hills on the other side of the coast highway, in Malibu.

Half a dozen years before the California Coastal Act of 1976 made it official, something primal already assured us that access to the beach should be welcomed, not off-limits like some tycoon’s yacht. So, with a wicked old chain-link fence blocking direct access to the shore, we ignored the signs and plunged under PCH.